Fish behavior observing water tank

The utility model discloses a fish behavior observing water tank. The fish behavior observing water tank comprises a rectangular water tank body, wherein the water tank body is divided into an upper layer of water tank and a lower layer of water tank by a separating layer; the upper layer of water tank and the lower layer of water tank are communicated with each other by a water way to form a loop; a screw propeller is arranged in the lower layer of water tank; a wedge-shaped cabin separating plate which separates the upper layer of water tank into a constant-cross section water tank and a variable-cross section water tank is arranged nearby the middle line of the upper layer of water tank; a front separating net is arranged nearby a wedge-shaped sharp end of the cabin separating plate; a flow-rectifying plate is arranged nearby the front end of the front separating net; a rear separating net is arranged nearby the foundation part of the wedge-shaped structure of the cabin separating plate; observing windows are formed in the two sides of the upper layer of water tank. After water flow is pushed by the screw propeller to flow through the lower layer of water tank to get to the flow-rectifying plate, laminar flow is formed, and under the action of the cabin separating plate, two tunnels, i.e. a constant-cross section tunnel and a variable-cross section tunnel are formed. Trails can be observed through the observing windows, and the behaviors of fishes can also be observed through vision of a computer. The fish behavior observing water tank has the advantages that different cross section flows can be simulated, the process is intuitive and reliable, and the laminar flow is stable.